In many industries, the design, analysis, development and production of sheet metal surfaces comprise a substantial portion of component manufacture. The most prevalent manufacturing process for sheet metal components is press forming. In spite of its widespread use, press forming practice has remained somewhat of an art, typically handled by experienced tooling engineers and designers. This is due to the fact that the physical process of press forming is not well understood. Complex interacting mechanisms and features such as friction, metal flow, material properties and boundary conditions make the press forming process difficult to analyze and predict.
In press forming, the initial flat sheet of material used to develop the final shape is called the blank. The main components of the press forming assembly are the punch, die, and the draw binder mechanism which controls the flow of the blank material inward to form the product. Design of this forming assembly is directly dependent on the surface definition of the final product. For a surface design to be manufactured without defects, the blank should be uniformly deformed by the descending punch without thinning or wrinkling. This process is influenced, to a large extent by the draw binder ring, which is placed outside the trim line, i.e., the boundary between the formed surface and surrounding scrap material. To locate the trim line, the designer must determine the boundary of the area on the blank which is affected by the forming process. This process is referred to as blank development. Besides binder-wrap design, the developed blank is also used for punch contact analysis, press forming layout, and as an indicator of material flow during the process.
Iterative redesign of a product which fails in production is very expensive in terms of time and capital investment. It would therefore, be highly useful for product designers to quickly determine the formability of the surface in the early stages of the surface design process. Detailed analysis techniques such as the finite element method are computationally demanding and not amenable for an interactive design environment. Thus, there is a need for quick and qualitative tools which can guide a designer toward a successful design. The present invention provides a technique to bridge the gap between final design analysis and initial surface construction.